Natural radioelements and inert gases in solution in groundwaters have been applied to problems of groundwater flow and age measurement. The 4He content of groundwaters generally increases with age and in the Bunter Sandstone, Nottinghamshire, the 4He contents of groundwaters have been linearly related to 14C ages. In the Lincolnshire Limestone, the He contents of the groundwaters have been used to indicate mixing of recharge water and interstitial water. In the other study areas, 4He and 40Ar in groundwaters have been used as qualitative indicators of age. The 4He contents of core samples have been related to the 4 He contents of the interstitial water and the formation depth. 4He diffusion in confined and non--confined sedimentary structures has been discussed. The amounts of non-radiogenic inert gases dissolved in groundwaters have been used to estimate groundwater recharge temperatures. In the Bunter Sandstone, these have been related to palaeoclimatic history by calibrating with the 14C ages. Estimated recharge temperatures have also been related to seasonal recharge, changes in the altitude of recharge and to variations in the hydrogen and oxygen isotopic ratios. Variation of the 222Rn contents of groundwaters has been used as an indicator of aquifer variability. The relative importance of intergranular and fissure flow and the variation in efficiency of 222Rn release into groundwaters has been investigated. The fraction of 222Rn released from rocks has been determined and the mechanisms by which 222Rn is released from sandstone, limestone and granite rock fragments has been discussed. Variability of the 226Ra contents of groundwaters has been explained in terms of the relative importance of the recoil and etch mechanisms of solution and the solubility of 226Ra salts in groundwaters.